Temperature compensating condenser



May 4, 1937- M. v. wr-:|s s 2,079,309

TEMPERATURE QOMPENSATING CONbENSER Filed May 14, 19:56

I I. NV-EN-1"OR I ATTORNEY Patented May 4, 1937 UNITED STATES amazon TEMPERATURE COMPENSATING CONDENSER Melvin V. Weiss, Haddonfleld, N. 1.,- assignor to Radio Condenser Company, Camden, N. J.

Application May 14, 1938, Serial No. 79,667

9 Claims.

This invention relates to a tuning condenser especially adapted for use in a superheterodyne type of radio receiver for use in aircraft work.

In radio receivers designed for aircraft, much attention must be given to the question of weight, without sacrificing mechanical strength and electrical stability.

Because of the dependence of aviation on radio signals, for directional beams, blind flying,

reports and the like, it is extremely important that the airplane receiver, when tuned to a given frequency, does not drift out of tune. The problem of receiver drift is especially diflicult in aircraft work because of the wide range of temperature encountered between ground level and high altitudes. Receiver drift is usually due to changes in the characteristics of the elements of the oscillator circuit, such as the tube, coil, resistors and more especially the tuning condenser because of ltsmetallic structure expanding and contracting when subjected to these wide and many times rapid temperature changes, brought about by the aircraft work.

In a gang condenser, used in a superheterodyne 23 aircraft receiver, the sections or units of the gang which tune the pre-amplifler circuits, variations in the capacity of these units, due to temperature changes, have the effect of reducing the overall sensitivity of the receiver but do not detune the receiver. Automatic volume control in the receiver will take care of the loss in sensitivity and maintain a constant audible output; whereas variations in the oscillator unit of the gang will detune the receiver.

85 It is therefore the principal object of my invention to provide a gang condenser for an aircraft receiver which, in general, has high rigidity but light weight, and one in which the oscillator unit is so constructed and arranged as to automatically compensate for a wide variation in temperature.

After much experimental work and many tests, I have found that by making the oscillator unit. and certain other parts of the gang condenser,

45 out of a material having a subs'tantiallyze'ro or very low temperature co-efllcient, and arranging these in the manner to be hereinafter described, I can get an oscillator condenser which will automatically compensate for a wide change in temperature, and will attain the general object of my invention, as well as other ancillary objects which will occur to one skilled in this art, on a reading of the specification and accompanying drawing.

' In the drawing:

(Cl. PIS-41.5)

Figure 1 is a plan view of a fourgang wildenser in which my invention is incorporated, a small section of one end of the condenser being broken away.

Figure 21s a part-vertical section and partelevational view on the line of the operating shaft of Figure 1.

Figure 3 is a side elevation of the gang condenser shown in Figures 1 and 2, with certain parts at the drive end being broken away.

Figure 4 is a fragmentary end view of the drive end of the condenser.

Figure 5 is,a perspective view of one of the condenser frame members.

Figure 6 is a perspective view of one type of support for the stator group of plates of one of the condenser units comprising the gang condenser.

Figure '7 is a perspective view of another type of support which may be used in place of the type of support shown in Figure 6.

In the various views, wherein like numbers refer to corresponding parts, i and 2 are the front and rear end plates of the frame of a gang condenser, four unit condensers being illustrated, as A, B, C and O. The frame members i and 2 are rigidly held together by substantial aluminum rods land 4, one of which is illustrated in perspective in Figure 5. The rods 3 and l are held to the end plate 2 through the medium of grooves I which are adapted to receive slots in the end plate 2, all as defined in application Serial No. 724,688, filed May 9, 1934, by Stanley S. Cramer.

The rods 3 and 4 are further bound together by shield and brace members 6, 1 and 8 fitting in cooperative grooves 0 in the rods 3 and l in a similar manner as described with respect to the end or rear bearing plate 2. Extending from the shield and brace plate 6 to the end plate 2, on opposite sides of the gang condenser below the rods 3 and 4, are metallic bars Ill and II, the plates 6, l and 8, and the end plate 2 being notched to-snugly flt over these bars l0 and ii,

and then afterwards, the metal at the junction is upset so as to securely anchor the bars to the said plates or framemembers.

Attached to the bars iii and il in any satisfactory manner, as by rivets or screws II, are m sulators ii, to the upper portion of which are attached, as by screws it, the tiebars carrying the stator groups of plates, all as set forth in Cramer Patent 1,800,719, issued April 14, 1931.

The rotor shaft is divided into two sections I5 and It. The section it, having a reduced end i1, is adapted to be force-fitted into the end of the section l5, which latter section carries the groups of rotor plates for the unit condensers A, B and C, while the section l8 carries the rotor plates for the unit condenser O, which illustrates an oscillator tuning condenser, whereas the unit condensers A, B and C are condensers for other tunable circuits associated with the oscillator unit. The stator group of plates of the oscillator unit 3 is carriei on a pair of brackets i8 and I8, as shown in Figure 6, or on a pair of studs as shown in Figure '2, which are independent of the bars it? and 65, as will be clear from Figure 1. When the brackets of Figure 6 are used, they are attached to the front end plate I by screws 26', preferably having large heads in order to get a large contact surface engagement with the plate I In the construction shown in Figure 7, the

stud 3.; has fiat sides 3! to receive one end of an insu ator i3 on one of these surfaces, the other end of the insulator ".ing fastened to stator tieba-r. The stud 36 has an annular shoulder engage the rear side of the end u plate and an annular dowel. or projection 36 of reduced diameter extending into the end plate The washer 3:3 and screw is entering the said dowel and shoulder to hold the stud 30 se curely in place on the end plate i.

The rotor shaft supported on the rear end plate 2 in any satisfactory manner as by a bushing 2? carried on a. plate 22 fastened to the end plates in any satisfactory manner as by screws 2-2. The front end of the shaft is likewise supported in any satisfactory manner on the front plate i, as by bushing Fwtened to operating end 25, as by set screws 26, is a collar Ti carrying a spring 28 which continuously acts to force the rotor shaft toward the end plate i. The usual rotor wipers are illustrated Since th'm gang condenser is designed particularly for aircraft use, lightness is an essential feature; hence, the rods 3 and 4, together with the rotor shaft portion 15 and the plates of the units A, B and C, are made of aluminum. The shaft IS, with the extensions i1 and 25, together with the end plates l and 2, as well as the shield and support plates 8, a and 8, and the bracket supports iii and i9, together with the rotor and stator plates for. the oscillator condenser plates G are made of a material having a substantially zero temperature coemcient, such as a steel having a composition of nickel and iron, where the nickel may be of the order of 36%.

While the use of this special material in the places mentioned somewhat increases the weight of the gang condensers over what it would be if only aluminum were used, it, together with the construction described, eliminates expansion and contraction due to changes in temperature which would ail'ect the operating characteristics of the oscillator unit. Since the stator plates, with their brackets shown in Figure 6, are carried on the mounting plate 1 and are all made of this special zero temperature coeillcient material, these parts will not be affected by the temperatures ordinarily encountered by an airplane. If the changes in temperature are sufllcient to affeet the heavy frame members 3 and l, causing them to expand longitudinally, this would carry the stator group of plates,.with the end plate I, in an endwise direction to the left, looking at Figure 1, but at the same time, the shaft I! would also expand longitudinally and the spring aovasoo 28 would carry the rotor shaft to the left along with and in substantially an equal amount with the stator plates, thereby keeping a substantially constant spacing between the stator and rotor plates. When these parts, that is, 3, I and I5, contract, the operation or movement of the stator and rotor plates of the oscillator condenser is in reverse direction.

While I have shown a four-gang condenser, the number of units in the gang may be varied to suit requirements, but in any case, the temperature compensating oscillator unit is arranged to be at one end of the gang.

What I claim is:

1. In a gang condenser comprising a frame including end memmrs and a unit condenser for tuning an oscillator circuit while the other units of the gang are used to tune amplifier circuits associated with the oscillator circuit, means for compensating in the oscillator unit for differences in temperature in which the condenser is used, said means including; unit plates, the stat: plates of which are separately supported c171 of said end frame members, the rotor she ing in two parts operatively connected lator unit rotor plates being on one portions, said stator and rotor uni, gether with that part of the shaf rr rotor: plates, the stator supports and at le" end frame member carrying said being made of a material having substan zero temperature co-efiicient, mea. continuously on the-gang rotor shaft to toward the end frame member carrying one said oscillator stator supports. I

2. In a single-control gang condenser having an operating shaft, comprising a frame ing end members for: carrying rotor and stator group units of plates, the rotor plates carried on said shaft one of said sets of group units being adapted for use in tuning an oscillator circult, while the other group units are used in other tunable circuits associated with the oscillator circuit, means for compensating in the oscillator unit for difference in temperature in which the condenser is used, said means including stator and rotor plates for the oscillator unit made of material having a very low temperature co-eillcient, and individual mounting studs for the oscillator stator plates attached to one end frame member, all of the same kind of material as the unit plates, that part of the shaft for the oscillator rotor plates also being of the same kind of material as the unit plates, and means acting continuously on the gang rotor shaft to move it toward the end frame member carrying the said oscillator stator supports.

3. In a gang condenser as set forth in claim 2, further characterized in that the said frame has, between said units, shield and brace members which, with both end frame members carrying the entire rotor shaft, are made of very low temperature co-efllcient material, the same as the oscillator unit plates.

4. In a gang condenser comprising a frame including end members and a unit condenser for tuning an oscillator circuit while the other units of the gang are used to tune amplifier circuits associated with, the oscillator circuit, means for compensating in the oscillator unit for differences in temperature in which the condenser is used, said means including; unit plates, the stator plates of which are separately supported on one of said end frame members, the rotor shaft being in two 2,079,309 parts force-fitted together,

said oscillator unit rotor plates being on one of said shaft portions, held together by a 5 tallic members, while the said plurality of light-weight methe rotor shaft for all the and members being rotor plates in the amplifier condenser units is also of light-weight metallic material, while the stator with its supports the oscillator unit, plates, shield plates,

together rotor shaft portion carrying and the rotor plates of with both frame end the rotor plates, are all made of, a material having substantially a zero temperature co-emcient, and means acting continuously on the gang rotor shaft to move it toward the end frame member carrying the said oscillator stator supports.

5. In a gang condenser comprising a frame including end members and a unit condenser for tuning an oscillator of the gang are used circuit while the other units to une amplifier circuits associated with the oscillator circuit, means for compensating in the oscillator unit for differences in temperature in which the condenser is used, said means including; ent supports for the stator tor unit, said supports being fastened to one end frame end members being frame member, the

a pair of independplates of the oscillaheld together with a plurality of light-weight,

rigid members, a rotor shaft for the gang, that part which carries the oscillator rotor plates,

30 together with the rotor and their supports,

gang rotor plates, the stator plates and at least the end member carrying said supports, all being of a material having substantially a zero cient, and means acting continuously on the shaft to move it toward the end temperature co-emframe member carrying the said oscillator stator supports.

6. In a gang condenser having stator and plates being carried on a includins an oscillator unit.

for changes in tempera- 4 rotor shaft and means for compensating receiver including, a

may be subjected in aircraft,

rotor of said unit made of material having a very low temperature co-efficient, the stator plates having an independent metallic support of the same material, while at least that part of the rotor shaft carrying the unit rotor plate is also of the same material with means acting continuously on the gang rotor shaft to move it toward the end frame member carrying the said oscillator stator supports.

7. A gang condenser as set forth in claim 6, further characterized in that the supports for the rotor shaft at both ends, and the shield plates between units of the gang are of the same special material as the stator and rotor plates.

8. In a gang condenser for an aircraft radio frame carrying amplifier tuning units andan oscillator unit, means for preventing the oscillator unit of the gang from detuning the receiver because of changes in temperature to which the receiver may be subjected, said means including frame supports for the stator plates of the oscillator unit independent of the frame supports for the other units of the gang, a special shaft portion for the rotor plates of the oscillator unit; the stator and rotor plates of said stator frame supports and said special rotor shaft portion, all being made of a material having a very low temperature co-emcient, and means acting continuously on the gang rotor shaft to move it toward the end frame member carrying the said oscillator stator supports.

9. A gang condenser as set forth in claim 8, further characterized in that at least the end frame member carrying the special rotor shaft portion is made of the same kind of material as the oscillator unit plates.

MELVIN V. 

